Mercruiser 120 water in oil after 6 hrs of breakin on new rebuild?????

[mike460]

Hello everyone, Just put in a new rebuilt engine in the boat and checked oil after the 3rd time out and found it to be milky? Boat has new manifold on it and good riser (but not new). It did seem to start hard the first time on the 3rd trip out but good after that. Then found the oil when back at the dock after only 2 hrs on the water. Please help. What do I look for? Did we burn the bearings up already?

 

[Bondo]

Re: Mercruiser 120 water in oil after 6 hrs of breakin on new rebuild?????

Ayuh,.... Welcome Aboard,.... Who rebuilt it,..?? was the block checked for Cracks,..??

 

[mike460]

Re: Mercruiser 120 water in oil after 6 hrs of breakin on new rebuild?????

Our local engine machine shop did all the machine work and assembly. The block was cleaned and baked and checked for cracks along with the head. It has all new components. Is it possible the block cracked after 5 hrs run time? If it was cracked wouldnt we have seen water in oil right away? It is a 72 Mercruiser 120hp, in a 76 star craft islander.

 

[mike460]

Re: Mercruiser 120 water in oil after 6 hrs of breakin on new rebuild?????

We plan to pull plugs tonight and inspect and also change oil and run it again on the muffs. Can water be forced up that far from backing it in too fast? What are the easiest things to check?

 

[JAKE 11]

Re: Mercruiser 120 water in oil after 6 hrs of breakin on new rebuild?????

Hi I am Jake11 Seal your head bolts.I had same problem and was told to use permatex # 2.It worked.I am so happy.
I have a 1974 starcraft i/o 120hp mercruiser.

 

[mike460]

Re: Mercruiser 120 water in oil after 6 hrs of breakin on new rebuild?????

Yes that was it. Had a marine mechanic take a look and found the problem for us since we were too busy and just want to fish. Thanks for your help